Immediately following the release of the Microsoft Surface in November, Microsoft sent its Windows head Steven Sinofsky packing. Just a couple of months later, he is already trying out a new platform: iOS.

We were tipped to a tweet from Sinofsky (@stevesi) from January 11th that was sent from Twitter for iPhone. We soon discovered a second tweet from the same platform on January 4th. Sinofsky is still tweeting from his Microsoft Surface and the Web, but we don’t see as many Windows Phone-based tweets as we do earlier in his Twitter timeline.

It is precisely what you say “Who knows, maybe he is just evaluating the competition some will say.”.
I have owned every iphone released (and every ipad and galaxy and kindle). It is far better to actually use a product day in and day out so before CES I started using it and will use it for a month or so. Just prior I was using my 920.
In Office I spent a long time using SmartSuite or Google Docs for the same reasons.